Pointing devices such as "mice" allow users to move quickly from one task to another, or between documents with great ease. However, the use of such a device must be within certain limits. The most common use occurs with a personal computer by a single user. The mouse has a wire that connects it with a central processing unit, which relays the position of the cursor to the unit for inputs and tracking. The screen has an arrow or some other kind of cursor for the user's convenience to see the position of the cursor. The computer does not use this arrow or cursor, relying instead on the wired-in inputs.
In larger displays, such as meeting room displays, pointing devices function in much the same way as the smaller versions. Instead of the screen having a limited size, the computer display projects onto a screen where several people can view it. Pointing devices send their inputs to the CPU in much the same way through a wire. The cursor on the screen again only serves the user's convenience.
The CPU tracks the cursor position in this large wired-in mouse by time or triangulation. In the time tracked systems, the CPU monitors where in the raster scan of a CRT an input occurs, then processes that information for the appropriate screen and task response. Triangulation occurs in the unwired systems. Previous to the mouse's use, two sensors have been placed in the room, which constantly triangulate the position of the device and it's relative coordinates on the screen, and then communicate these to the CPU.
A problem occurs in these pointing devices when the system no longer has a rasterized display. Spatial light modulators such as liquid crystal displays (LCD) and digital micromirror devices (DMDs, also known as deformable mirror devices) have made great leaps in acceptance as display technologies. Since they do not have a rasterized format, the CPU can no longer track the mouse position in the same way.
For the smaller systems, with one user and a hard-wired mouse, the system functions in the same way, using the sensors on the mouse to send the position of the cursor. Instead of the position being a certain point in a rasterized display, it would now be the position on an x-y grid. Spatial light modulator as well as certain other displays have an x-y grid of individual elements that create the picture. However, in the large displays, the time systems are no longer functional, and the triangulation becomes much more difficult.
A need arises, therefore, for a pointing device that can perform with large, spatial light modulator, or other x-y grid type displays.